Wellbore encasement

ABSTRACT

A method of encasing a wellbore is provided comprising the application of 3D printing technology to apply a series of layers of lining material to the interior surface of a wellbore. The layers may be of different materials to make best use of their different material properties, to provide structural integrity and good sealing properties, for example. Through suitable printhead control, specific structural features such as channels for receiving measurement, power or communications equipment may be incorporated into the lining structure. Associated devices for depositing the layers of lining material are also provided.

FIELD OF THE INVENTION

The present invention relates to the encasement of wellbores, and inparticular to methods of depositing cement into an annulus between anewly-drilled borehole and reinforcing casing within the borehole.

BACKGROUND TO THE INVENTION

Conventionally, newly-drilled boreholes are reinforced by the insertiontherein of a casing, which may comprise steel or concrete pipes, toprovide structural integrity to the wellbore. Such casings are typicallyslightly smaller in diameter than the drill string and are secured inplace by pumping cement into the annulus formed between the outersurface of the casing and the borehole.

As illustrated by reference to FIG. 1, cementing is usually performed bycirculating a cement slurry through the inside of the casing and outinto the annulus through a casing shoe at the bottom of a casing string.In order to deposit a correct quantity of the cement slurry on theoutside of the casing, a plug is pumped with a displacement fluid behindthe cement slurry column. When the plug reaches the casing shoe itblocks the flow path of the cement slurry and prevents further flow offluid through the shoe. This stage can be seen at surface as a pressurespike at the cement pump. To prevent the cement from flowing back intothe inside of the casing, a float collar above the casing shoe acts as acheck valve and prevents fluid from flowing up through the shoe from theannulus.

Cementing is supposed to form an impenetrable seal to keep hot, gassyoil from surging up the well. However, as is well documented, a singleflaw in that seal, perhaps a crack the size of a human hair, can beenough to cause a catastrophic leak. One known failure mechanism,suspected of being the cause of the Deepwater Horizon catastrophe, isgas bubbles getting into the cement and forming channels for pressurisedgas or oil to surge uncontrollably up the well. The gas bubbles couldoriginate from the initial cement slurry mix, which may includenitrogen, or could leak in through the borehole wall while the cementslurry is setting.

As illustrated by reference to FIG. 2, another known cause forinadequate cementing is because of the non-uniformity of the boreholewalls. A predetermined volume of cement may be calculated for pumpinginto the wellbore to fill the annulus to a specific height. This can beproblematic if the borehole wall includes voids or fissures, increasingthe volume of the annulus over that expected such that the predeterminedvolume of cement would not reach the desired specific height. This hasbeen overcome by top-up cement pumping operations to fill the spacebetween the actual height of the cement in the annulus and the desiredheight.

Because of the extreme conditions that can be found in oil wellbores, itis important to monitor those conditions and their effects on thewellbore cement. Factors requiring monitoring can include cementintegrity, cement placement, cement strength, and cement impermeability.

Important variables include stress/strain (providing information aboutgeomechanical forces that may affect cement curing and bonding),pressure and temperature (being strong indicators of gas or liquidmovement). Further parameters for monitoring include pH and gas/liquidphase. Accordingly, downhole sensors can be placed to monitor thesevariable parameters. Existing sensor technologies include distributedsensors, which use a fibre optic cable to take measurements along thelength of the cable, which acts as both sensor and communication mediumto relay the sensed data to the surface.

Another type of sensor is passive wireless sensor tags, which can beplaced in hostile environments and which relay sensed data wirelessly toa transceiver at the surface and which require no power source.

A problem encountered in depositing cement in the annular gap betweenthe casing and the wellbore surface is that residual drilling mud andmud filtrate cake can be stuck to the casing and formation which reducescement bonding effectiveness. Accordingly, pre-cementing flushes canused to wash out the remaining drilling mud and remove the mud filtratecake.

Another problem encountered in wellbore cementing is centralising thewellbore casing. One purpose of a casing centraliser is to act tosupport and centre the casing in the wellbore, so as to allow cement tobe pumped up the annulus with least resistance around the casing andproduce a robust cement seal, ensuring zonal isolation. If thecentraliser is not strong enough to centre the pipe, or if it breaks,the consequences can be very expensive. If it breaks in a deviated well,centralisation is usually completely lost, rendering effectivecementation impossible. Furthermore, the centraliser may jam the pipedown hole.

Whereas the above description of the prior art has focused on oil welltechnology, many of the principles apply to other types of wellbore,such as water wells. These may be of much larger diameter but shallowerthan oil well boreholes, but which must also be structurally sound.Rather than being at risk of high pressure fluids escaping through acasing, the walls of water well boreholes may be liable to inwardcollapse.

As such, there is a need for an improved method of encasing wellbores,and an associated need for a wellbore encasement device. There isfurthermore a need for the provision of improved wellbore monitoringsystems.

It is known to construct complex 3D structures through 3D printing, alsoknown as additive manufacturing (AM), which comprises building up layersof material one after the other via a nozzle head that is controlled to‘print’, i.e. deposit, the material. It is known to use such AMtechniques to construct structures out of cement (concrete), asdiscussed for example in ‘Development of a Viable Concrete PrintingProcess’ by Sungwoo Lim of the Department of Civil & BuildingEngineering, Loughborough University, UK. AM processes have advantagesover conventional construction and manufacturing processes in that theydo not require moulds, they offer design freedom, and they have thepotential to include additional functionality into structures.

AM is in its infancy, especially when applied to the construction ofconcrete structures, and it has not been applied in the context ofwellbores.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda method of lining a wellbore comprising the steps of:

-   -   inserting a directional nozzle into the wellbore; and    -   controlling the direction of the nozzle and controlling flow        through the nozzle to deposit at least one layer of lining        material onto the interior surface of the wellbore.

The present invention provides a very effective method of lining awellbore that applies 3D print technology to down-hole applications.Because the nozzle can be controlled both in terms of direction and flow(i.e. on/off, or to varying degrees between those extremes), the liningmaterial can be deposited in a highly controlled and direct manner. Thisovercomes disadvantages with the known cement slurry pumping operations,and enables the exploitation of advantageous features of 3D printingtechnology.

The direction of the nozzle may be controlled so as to rotate about thelongitudinal axis of the wellbore, for lining an entire circumference ofthe interior surface of the wellbore. The nozzle direction may furtherbe controlled to be displaced along the longitudinal axis of thewellbore, for lining a length (height) of the wellbore. In someembodiments, the nozzle may be rotated relative to the longitudinal axisof the wellbore. Accordingly, it is possible to control the depositionof the lining material with precision to a specific target area.

The method preferably comprises depositing multiple layers of liningmaterial onto the interior surface of the wellbore. This enables theexploitation of the benefits of a layered structure, providing animproved structural integrity to the lining.

In some embodiments, the nozzle is controllable to deposit differentmaterials. Thus, different areas of the wellbore may be lined withdifferent materials, or portions may be lined with multiple layers ofdifferent materials, so exploiting the advantages that can be obtainedthrough the different properties of those materials, and the synergisticeffects of combining them.

Multiple nozzles may be inserted into the wellbore, each controllable todeposit a different respective material. Typically, the multiple nozzlesare mounted on a common printhead.

Different materials considered for application to the wellbore inmethods of the invention include reinforcing materials such as cement,concrete, resins, plastics, metals, ceramics, and the like, and sealingmaterials such as rubber, plastics, bitumen, neoprene, and the like.

Although in some embodiments the lining material is deposited directlyon to the interior surface of the wellbore and that deposited materialforms the entire lining of the wellbore, in other embodiments a casingpipe inserted into the wellbore forms the final interior surface of thewellbore and the method is used to deposit the material into an annulargap formed between the interior surface of the wellbore and an exteriorsurface of the casing pipe. For the latter embodiments, the methodincludes a step of inserting a casing pipe into the wellbore, typicallybefore the directional nozzle is inserted into the wellbore. Thedirectional nozzle may be inserted through the interior of the casingpipe or, alternatively, on the exterior of the casing pipe.

When inserted through the interior of the casing pipe, the directionalnozzle exits at a bottom end of the casing pipe and the nozzle iscontrolled to point towards the area of the wellbore surface to belined.

The lining may be built up in radial layers, with the nozzle directedgenerally radially outwards. Alternatively, the lining may be built upin axial layers, with the nozzle directed generally upwards ordownwards, depending on whether those axial layers are built up fromabove or from below.

To assist in depositing axial layers, the method may include a step ofinserting a bung between the casing pipe and the interior surface of thewellbore, wherein the step of controlling the direction of the nozzleand controlling flow through the nozzle comprises depositing the atleast one layer of lining material onto the bung and thereby ontointerior surface of the wellbore.

In some embodiments, the topography of the borehole is determined, andthe control of the direction of the nozzle and the control of the flowthrough the nozzle being dependent on the topography. This enables abespoke deposition of the lining material to account for irregularitiesin the wellbore surface.

The method may include a step of accelerating a cure of the depositedmaterial prior to deposition of a subsequent layer, so as to speed upthe lining process whilst ensuring material integrity.

According to a second aspect of the present invention there is provideda device for depositing at least one layer of material onto an interiorsurface of a wellbore, comprising:

-   -   a directional nozzle;    -   a source of material in connection with the nozzle;    -   means to control the direction of the nozzle; and    -   means to control the passage of the material through the nozzle,        whereby to deposit at least one layer of lining material onto        the interior surface of the wellbore.

The nozzle may be mounted for some or all of: rotation about a verticalaxis, displacement along a vertical axis, and rotation relative to avertical axis.

In some embodiments, the nozzle is selectively in connection withmultiple sources of different materials, whereas in other embodimentsthe device comprises multiple nozzles, each in connection with adifferent respective source of material. In either instance, the deviceenables the deposition of different materials to take advantage of theirdifferent properties, particularly when combined.

The or each nozzle may be mounted on a common printhead, facilitatingpositioning of the nozzle(s) at the deposition site.

As described above in the context of the first aspect of the invention,in some embodiments a wellbore will be lined with a casing pipe, and thelining material deposited to fill the annular gap between the outside ofthe casing pipe and the inside of the wellbore surface.

For such embodiments, the device may be configured for insertion througha wellbore casing pipe. Typically, the or each nozzle is mounted on anarm that is able to bend so as to position the nozzle directed generallyupwards into the annulus between the wellbore casing pipe and theinterior surface of the wellbore, for deposition of axial layers oflining material from beneath. To facilitate this, the at least onenozzle may be connected to the associated source of material via aflexible conduit.

Alternatively, the device may be configured for insertion over awellbore casing pipe, between the exterior of the wellbore casing pipeand the interior surface of the wellbore. Typically, the or each nozzleis mounted on a ring having a diameter substantially matching that ofthe wellbore casing pipe so as to position the nozzle directed generallydownwards, for deposition of axial layers of lining material from above.Alternatively, the nozzle may be directed generally outwards, for thedeposition of radial layers.

The device may include multiple printheads positioned at regularcircumferential intervals, so providing faster deposition of materialsand requiring less rotation of the device about the longitudinal axis ofthe wellbore for lining an entire circumference of the wellbore.

A controller is preferably included in the device to control thedirection of the nozzle and the flow of material through the nozzle. Thecontroller is preferably programmable, typically so as to deposit thematerial along an optimum path. In preferred embodiments, the deviceincludes means for determining the topography of the borehole, and theoptimum path is determined at least partly on the basis of thedetermined topography. The topography of the borehole may be determinedelectronically, such as via an emitter and associated detector, such aslaser, radar, or the like, or may be determined mechanically, such asvia a contour wheel.

In some embodiments, the device includes a UV source or other means foraccelerating the curing of the deposited material.

Through suitable control of the operation of the nozzles, the lining maybe built up in multiple layers and of different materials, and mayinclude strategic voids in the final structure. Such voids can be usedto place sensors or may run along a length of the wellbore for receivingcables—either for structural reinforcement or for monitoring purposes(e.g. fibre optic cables).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings, in which:

FIG. 1 shows a prior art wellbore cementing process;

FIG. 2 shows an irregular surfaced borehole and resultant incompletecementing;

FIG. 3 shows a wellbore lined with multiple layers using a process ofthe invention;

FIG. 4 shows a detail view of a portion of the layered structure of FIG.3;

FIG. 5 shows a device according to one embodiment of the invention fordepositing material into the wellbore;

FIG. 6 shows a dual media extrusion achievable using the device of FIG.5;

FIG. 7 shows a device according to another embodiment of the inventionfor depositing material into the wellbore;

FIG. 8 shows a device in situ in a wellbore and depositing a series ofaxial layers of material;

FIG. 9 shows a device according to another embodiment of the inventionfor depositing material into the wellbore;

FIG. 10 shows a device according to yet another embodiment of theinvention for depositing material into the wellbore;

FIG. 11 shows a device according to even yet another embodiment of theinvention for depositing material into the wellbore;

FIG. 12 shows an alternative application of a device according to theinvention, for repairing casing walls;

FIG. 13 shows a device according to a further alternative embodiment ofthe invention for depositing material into the wellbore; and

FIG. 14 shows deposition of material using the device of FIG. 13.

DETAILED DESCRIPTION

In simple terms, the invention relates to the concept of depositinglining material to wellbores using 3D printing technology. A mediadispensing apparatus including at least one nozzle is inserted down aborehole for depositing multiple layers of lining material to theinterior surface of the borehole in a controlled manner. One embodimentis shown in FIGS. 5 and 8, in which the nozzle is mounted via auniversal joint to a distal end of a hollow support rod. The support rodcontains a primary flexible conduit for fluidly connecting the nozzlewith a source of a first lining material. The support rod furthercontains a secondary flexible conduit for fluidly connecting the nozzlewith a source of a second lining material, different to the first. Asshown in FIG. 6, the nozzle and the conduits may be arranged to dispensethe first and second materials simultaneously, in a form of extrusion.In other embodiments, only a single source of material is connected tothe nozzle.

In certain embodiments, multiple different material sources may beconnected to a single nozzle. The different sources may be selectivelydispensed through the nozzle, for example through a selective valveblock. In other embodiments, there may be multiple nozzles eachconnected to one or more sources of material.

The direction of the or each nozzle can be controlled so as to directthe flow of material through the nozzle at a desired target area. Theflow of material through the or each nozzle can also be controlled,either by means of a binary on/off valve or by a variable valve.

The control of the nozzle operation is performed by a programmablecontroller, which may be within the printhead or remote therefrom. As isknown in the art of 3D printing, material is deposited in layers builtup one upon another to form a 3D structure. To ensure that the integrityof the structure is not compromised, it is important for the previouslayer on which a subsequent layer is being deposited to have ‘gone off’or cured, thus having sufficient strength to support the new layerwithout deformation. The curing time will be dependent on a number offactors, including the material being deposited, the thickness of eachlayer, and environmental conditions. The process may be accelerated bysuitable means, such as the illumination of the layer by UV light.

In one embodiment, as shown in FIG. 8, the support rod is inserted intothe wellbore to position the nozzle facing outwards towards the interiorsurface of the wellbore. The support rod may be held centrally in thewellbore by suitable centralizer means, as are well known in the art.

A first layer of lining material (e.g. cement) is deposited via thenozzle by rotating the support rod 360° about a longitudinal axis of thewellbore with the nozzle valve open. The longitudinal axis wouldtypically be approximately vertical, but could be off vertical or evenbe horizontal. The deposited layer of material forms a ring around thecircumference of the wellbore. The support rod is then raised toposition the nozzle above the previous layer for depositing a subsequentlayer above the previous one. The rings of lining material are thusbuilt up axially from the bottom up to define a substantially contiguouslining. By being constructed of a series of essentially discrete layers,the rings of lining material act akin to the packing rings of a stuffingbox, providing enhanced sealing properties and therefore improvedresistance to the sort of catastrophic failure associated with ablow-out from gases escaping through imperfections in the liningstructure.

In preferred embodiments, the axial rings may be built up in sections ofdifferent materials, as illustrated in FIGS. 3 and 4, which shows asection of the wellbore lined with axial strata of concrete, rubber orthe like, foam and resins. As will be understood, the materials andtheir arrangement may be selected to make best use of their materialproperties, such as structural or sealing properties.

In addition, each axial ring could itself be formed of multiple layersof lining material, built up radially from the outside in. Again, thosedifferent layers could be formed of different materials.

As well as or instead of using fundamentally different materials, thelayers can be built up of essentially the same materials but withdifferent properties—such as cements of different densities.

A detail of the ‘printhead’ of a modification of the embodiment of FIGS.5 and 8 is shown in FIG. 7. This modified embodiment includes adjustablehinged guides at the nozzle outlet to assist in directing the flow ofmaterial from the nozzle to ensure that the material is deposited at theintended location.

The programmable controller control operation of the nozzle to depositthe lining material(s) according to the topography of the wellbore. Thetopography may be determined by different means, which may beincorporated into the printhead or be independent thereof. Examples ofsuitable topography-determining means include: a camera or otherscanner, laser, radar, or the like, or a mechanical contour wheel.

Multiple printheads may be mounted to a single support arm, typically atregular circumferential intervals. For example, two printheads may bemounted 180° apart for dispensing material to opposite sides of thewellbore simultaneously, thus reducing by half the time to cover theentire circumference and also only requiring a 180° rotation of thesupport arm. The printheads need not be in the same plane as oneanother.

One particular advantage of 3D printing is the ability to form voids atspecified locations. As shown in FIGS. 3 and 4, vertical channels (i.e.parallel to the longitudinal axis of the wellbore) can be formed in thelining structure for receiving wellbore monitoring, power, andcommunications equipment. One application would be to receive fibreoptic cables for a distributed sensing system as described in theintroduction. Another option would be to form pockets, either incommunication with the channels or independent thereof, for receivingsensors such as the passive wireless sensors described in theintroduction. The printhead could insert these sensors from a cartridgeof them. It could insert them at predetermined distances, pressures,etc. It could locate more into regions of the wellbore where it is morecritical to collect data.

In addition or instead of receiving the monitoring, power, andcommunications equipment, the channels could receive reinforcingstructures, such as structural fibres, steel cables, extruded fibres,and the like.

The cables or fibres can be inserted into the channels during thedeposition process, for example by being unloaded from spools, or couldbe inserted after the entire channel has been formed. For somestructures, the cable could be extruded at the printhead during thedeposition of the lining material(s). A heater may therefore be providedon the printhead for extrusion operations.

For other applications, the channels may be filled with a stent-likematrix, formed for example of sintered metal, which may be deposited atthe same time as the rest of the lining material. The matrix can then befilled with a suitable material, such as a resin, to fill voids in thematrix and provide a structurally rigid reinforcement through the liningstructure.

In some embodiments, and especially where the apparatus is used to fillthe annular gap between a wellbore casing and the wellbore interiorsurface, rather than building the ring-like layers up from the bottom,the layers can be built up from the top down. To achieve this, thedelivery device with the printhead is inserted down the interior of thecasing. Exemplary embodiments are shown in FIGS. 9 to 11.

In the embodiment of FIG. 9, two printheads are inserted through thecasing, each with a flexible conduit connecting a nozzle to a source oflining material at the surface. Each printhead is delivered to thedistal end of the casing where it exits and, by virtue of theflexibility of the conduit and through a suitable drive system—which mayincorporate wheel driven tracks—is able to be steered back on itself todirect the nozzle to point generally upwards. A flexible umbrella-likemembrane structure is supported on the printhead surrounding the nozzleand is adapted to conform to the topography of the borehole to accountfor variations therein and to support the layer of material beingdeposited.

Each layer is deposited from below onto the bottom of the layer above.To provide a first layer onto which to deposit the subsequent layers,the printhead includes a mechanism for inserting a bung in the annulargap. One way to provide the bung is through use of an expandingfoam-like material, which may be deposited in the gap by a two-packresin module in conjunction with an aerosol. The resins and aerosol maybe incorporated into the printhead and be operated under the control ofthe programmable controller. On actuation, the resins will be dispensedand mixed under the propulsion of the aerosol, thereby expanding from anoutlet of the module. The foamy mixture will quickly harden sufficientlyto support deposition of layers of the lining material onto its bottomsurface.

Due to a partial vacuum and by virtue of inherent surface tension of thematerial being deposited, each layer will remain where deposited andwill not for example drop due to gravity.

When depositing the lining material layers in water from below, thewater may act to help keep the deposited material in place, if thatmaterial is buoyant in the water. In addition, the lining material(s)may be selected so that they are activated by contact with water, toaccelerate the curing process or to improve adhesion, to expand, or toheat up, for example.

An alternative embodiment is shown in FIG. 10, in which the printheadhas sprung tracks that conform to the gap between the casing and theinterior surface of the wellbore.

Other alternative embodiments are shown in FIG. 11. One of theprintheads shown here on the left may be guided by multi-positionalwheels and by the reaction forces from the expulsion of a water jet froman end opposite to the nozzle for depositing the lining material.Instead of a water jet, the embodiment shown on the right uses animpeller or propeller to urge the printhead upwards.

In an alternative implementation, illustrated in FIGS. 13 and 14, ratherthan being sent down the inside of the wellbore casing, the printhead issent down the outside of the casing. In this embodiment, the printheadcomprises a ring structure, having a central aperture sized to bereceived around the casing. Conduits are connected to circumferentiallyspaced nozzle outlet vents through the ring structure for the deliveryof lining material to deposit layers of the material into the gapbetween the exterior of the casing and the interior surface of thewellbore, from the bottom up. The printhead includes a drive unitincorporating wheels bearing against the exterior of the casing to drivethe printhead vertically and rotatably, for example in a helical risingmovement.

In any of the embodiments, the printhead can be adapted to act as a highpressure water/air/other fluid/gas jet to remove residual drilling mudto ensure a clean surface for the application of the lining layer(s).

An advantage of the provision of a nozzle whose direction of depositionof material may be controlled, and especially when mounted on aprinthead that is directed into the annular gap between the casing andthe interior surface of the wellbore is that it will allow thecentralisation of the casing by several means. The very fact that theprinthead is circulating around the outside of the casing will force thecasing away from the surface of the wellbore, and when so spaced, thelining materials are deposited so as to keep the casing spaced away fromthe wellbore surface. Additionally, just by directing the printhead (orat least the nozzle(s) thereon) in a particular area, the reaction forceof the material being ejected from the nozzle(s) will force the casingaway from the wellbore surface.

One further application of the technology is in the repair of wellborecasings. As shown in FIG. 12, a printhead may be positioned to direct anozzle towards a damaged or defective section of the casing. Materialcan be injected from the nozzle through the defect thereby filling itmuch like a rivet.

It will be understood that aspects of the various embodiments describedabove may be combined with aspects of other embodiments to providefurther alternative implementations.

Whereas the above detailed description has been made in the context ofoil wellbores, the technology can be applied to other application. Oneexample is a large-diameter groundwater well, traditionally lined withbricks or with pre-cast sections of concrete pipe, which may be linedinstead using the cement printing techniques, particularly of the typeshown in FIG. 8. Another example is for the sealing of sewers. For suchsimple applications, just a single lining material may be used, althoughenhanced benefits may be obtained through combining multiple materials.

For some applications, at least one of the lining materials may comprisea reactive material that expands when certain conditions are met, suchas coming into contact with water or a particular temperature orpressure. This may be an outside layer of the lining, and be reactive tothe environmental conditions to break down over a predetermined period.For other applications, at least one of the lining materials may behydrophilic, allowing water to flow through it at a given rate. This maybe used in conjunction with a reactive substrate layer, wherein thereactive substrate reacts with the water.

1. A method of lining a wellbore comprising the steps of: inserting adirectional nozzle into the wellbore; and controlling the direction ofthe nozzle and controlling flow through the nozzle to deposit at leastone layer of lining material onto the interior surface of the wellbore.2. The method of claim 1, wherein controlling the direction of thenozzle comprises rotating the nozzle about the longitudinal axis of thewellbore.
 3. The method of claim 1, wherein controlling the direction ofthe nozzle comprises displacing the nozzle along the longitudinal axisof the wellbore.
 4. The method of claim 1, wherein controlling thedirection of the nozzle comprises rotating the nozzle relative to thelongitudinal axis of the wellbore.
 5. The method of claim 1, whereinmultiple layers of lining material are deposited onto the interiorsurface of the wellbore.
 6. The method of claim 1, wherein the nozzle iscontrollable to deposit different materials.
 7. The method of claim 1,wherein multiple nozzles are inserted into the wellbore, eachcontrollable to deposit a different respective material.
 8. The methodof claim 7, wherein the multiple nozzles are mounted on a commonprinthead.
 9. The method of claim 1, wherein the at least one materialis selected from the group consisting of cement, concrete, resins,plastics, metals, ceramics, rubber, plastics, bitumen, and neoprene. 10.The method of claim 1, further comprising a step of inserting a casingpipe into the wellbore.
 11. The method of claim 10, wherein the casingpipe is inserted into the wellbore before the directional nozzle isinserted into the wellbore.
 12. The method of claim 11, wherein thedirectional nozzle is inserted through the interior of the casing pipe.13. The method of claim 10, wherein the directional nozzle is insertedon the exterior of the casing pipe.
 14. The method of claim 10,including a step of inserting a bung between the casing pipe and theinterior surface of the wellbore, wherein the step of controlling thedirection of the nozzle and controlling flow through the nozzlecomprises depositing the at least one layer of lining material onto thebung and thereby onto interior surface of the wellbore.
 15. The methodof claim 14, wherein the at least one layer of material is depositedfrom above the bung.
 16. The method of claim 14, wherein the at leastone layer of material is deposited from below the bung.
 17. The methodof claim 10, further including a step of determining the topography ofthe borehole, the control of the direction of the nozzle and the controlof the flow through the nozzle being dependent on the topography. 18.The method of claim 10, further including a step of accelerating a cureof the deposited material prior to deposition of a subsequent layer. 19.A device for depositing at least one layer of material onto an interiorsurface of a wellbore, comprising: a directional nozzle; a source ofmaterial in connection with the nozzle; means to control the directionof the nozzle; and means to control the passage of the material throughthe nozzle, whereby to deposit at least one layer of lining materialonto the interior surface of the wellbore.
 20. The device of claim 19,wherein the nozzle is mounted for rotation about a vertical axis. 21.The device of claim 19, wherein the nozzle is mounted for displacementalong a vertical axis.
 22. The device of claim 19, wherein the nozzle ismounted for rotation relative to a vertical axis.
 23. The device ofclaim 19, wherein the nozzle is selectively in connection with multiplesources of different materials.
 24. The device of claim 19, comprisingmultiple nozzles, each in connection with a different respective sourceof material.
 25. The device of claim 19, wherein the or each nozzle ismounted on a common printhead.
 26. The device of claim 19, wherein thesource of material is selected from the group consisting of cement,concrete, resins, plastics, metals, ceramics, rubber, plastics, bitumen,and neoprene.
 27. The device of claim 19, configured for insertionthrough a wellbore casing pipe.
 28. The device of claim 27, wherein theor each nozzle is mounted on an arm that is able to bend so as toposition the nozzle directed generally upwards into the annulus betweenthe wellbore casing pipe and the interior surface of the wellbore. 29.The device of claim 28, wherein the at least one nozzle is connected tothe associated source of material via a flexible conduit.
 30. The deviceof claim 19, configured for insertion over a wellbore casing pipe,between the exterior of the wellbore casing pipe and the interiorsurface of the wellbore.
 31. The device of claim 30, wherein the or eachnozzle is mounted on a ring having a diameter substantially matchingthat of the wellbore casing pipe so as to position the nozzle directedgenerally downwards.
 32. The device of claim 25, comprising multipleprintheads positioned at regular circumferential intervals.
 33. Thedevice of claim 19, further comprising a controller to control thedirection of the nozzle and the flow of material through the nozzle. 34.The device of claim 33, wherein the controller is programmed to depositthe material along an optimum path.
 35. The device of claim 34, furthercomprising means for determining the topography of the borehole, whereinthe optimum path is determined at least partly on the basis of thedetermined topography.
 36. The device of claim 33, wherein thecontroller is programmed to deposit the material in multiple layers. 37.The device of claim 19, further comprising a UV source for acceleratingthe curing of the deposited material.